1. Field of the Invention
The invention relates to a communication system, ports of the communication system and a method for managing a communication system, all based on a ring network of two or more ports coupled preferably in daisy chain fashion to one another to allow communication.
2. Description of Relevant Art
The following descriptions and examples are given as background only.
A communication system is generally known as a system that permits communication between nodes interconnected by a transmission line. Each node can transmit information and receive information across the transmission line. The communication system of interconnected nodes can be organized in various topologies, such as bus, ring, star, or tree topology, or a combination thereof.
A bus topology network is generally regarded as linear. Transmissions from one node propagate along the transmission line and are received by all other nodes connected to that bus. A ring topology network, however, generally consists of a series of nodes connected to one another by unidirectional transmission links to form a single, closed loop. Examples of a ring network (also referred to as ring bus) are described in IEEE 802.5, Fiber Distributed Data Interface (FDDI) and the Media Oriented Systems Transport (MOST) specification.
The transmission line between nodes can be either wired or wireless, for example, copper wire, fiber optic, or wireless transmission medium for the chosen transmission line, respectively.
In ring bus systems, failure of a single node leads to failure of the entire network. For fault clearance, the failing node must be identified. If the fault can be identified by the controller of the failing node, it may be written into memory for later analysis. This is not possible, if the controller itself or other hardware, which cannot be monitored by the controller, fails. Such hardware may be the optical transmitter of an optical network.
U.S. Pat. No. 5,394,401 discloses a ring network based on a smart wiring concentrator or Multi-station Access Unit (MAU) to which individual network nodes are connected. Failure of a single node is detected by a controller. This solution requires a star wiring scheme from each node to the MAU. Furthermore the MAU requires one network port for each attached node, which makes this solution complex and expensive.
WO 99/12313 A discloses a local communication system and apparatus for use therein. This communication system detects bus failures and transmits a shutdown command to succeeding bus nodes.
US 2006/0026471 discloses a loop status monitoring apparatus which identifies failing devices in a network and stores information about these failing devices.
EP 0431635 discloses a ring type LAN having a fault processing system which activates loop-back circuits for the case a node fault has been detected.